1. Field of the invention
The invention relates to lightning protection systems for boats and more particularly is concerned with a lightning rod mounted on the top of a mast and a copper wire attached to the rod and running down the mast where it is attached to a retractable ground.
1. Description of the Prior Art
A major problem in connection with boats is that sailboat masts and radio antennas normally utilized in boating serve as points of incipient receipt of lightning strikes which cause serious damage to electrical equipment and to the structure of the boat as well, not to mention injury or even death to those on board. In the absence of efficient, economical, and reliable lightning protectors, boat owners are reluctant to venture out onto open waters whenever there is even a slight possibility of thunderstorms. In areas such as Southwest Florida and the Chesapeake Bay, for example, the NOAA weather forecasts predict thunderstorms on a daily basis. Thus, the boat owner must either stay at home or risk the possibility of being struck by lightning. Boats are particularly at risk because the mast or antenna becomes the highest point on the water and the most likely to attract a lightning charge.
Prior art devices have been made in various forms including long flexible chains or links of metal as disclosed in U.S. Pat. No. 11,217 to Forbes, a fixed ground attached to the hull as shown in U.S. Pat. No. 2,909,589 to Booker, a lightning arrestor comprising a reel that is rotatably mounted on the base on the boat and has a cable wound t as disclosed in U.S. Pat. No. 3,483,305 to Bonkowski et al., or a ground plate as disclosed in U.S. Pat. No. 3,919,956 to Invernizzi. The prior art devices suffer from the same problem that all underwater objects suffer and that is the incrustation of barnacles or other marine growth which then become insulating material and prevents the discharge of the electrical current caused by lightning. If the ground of a lightning protection installation is an unpainted metal plate permanently attached to the hull of a boat beneath the water line, the plate will become covered with marine growth, greatly reducing its effectiveness as a ground. If, however, the plate is coated with anti-fouling paint, the paint will serve as insulation, so again the plate loses its effectiveness as a ground. By making the ground retractable, it would be in contact with the water for only short periods of time, and therefore can be left unpainted without its acquiring marine growth. A through-hull installation is preferable to an over-the-side installation because the lightning is led in a straight line from the masthead to ground. Also, it is quickly activated and less cumbersome than dragging a metal plate or a tube through the water made fast to a metal wire.